Method of manufacturing a micro-electromechanical fluid ejecting device

ABSTRACT

A method of manufacturing a micro-electromechanical fluid ejecting device includes the step of forming a plurality of nozzle chambers on a wafer substrate. Sacrificial layers are deposited on the wafer substrate. A plurality of fluid ejecting mechanisms is formed on the sacrificial layers to be operatively positioned with respect to the nozzle chambers. The sacrificial layers are etched to free the fluid ejecting mechanisms. The fluid ejecting mechanisms are formed so that they are capable of ejecting fluid through both of a pair of fluid ejection ports defined in a roof of each nozzle chamber on one cycle of operation of the fluid ejecting mechanism.

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, US patent applications identified by their US patent application serial numbers (USSN) are listed alongside the Australian applications from which the US patent applications claim the right of priority. US PATENT/ PATENT APPLICATION AUSTRALIAN (CLAIMING CROSS-REFERENCED RIGHT OF PRIORITY AUSTRALIAN FROM AUSTRALIAN PROVISIONAL PATENT PROVISIONAL DOCKET APPLICATION NO. APPLICATION) NO. PO7991 09/113,060 ART01 PO8505 09/113,070 ART02 PO7988 09/113,073 ART03 PO9395  6,322,181 ART04 PO8017 09/112,747 ART06 PO8014 09/112,776 ART07 PO8025 09/112,750 ART08 PO8032 09/112,746 ART09 PO7999 09/112,743 ART10 PO7998 09/112,742 ART11 PO8031 09/112,741 ART12 PO8030  6,196,541 ART13 PO7997  6,195,150 ART15 PO7979 09/113,053 ART16 PO8015 09/112,738 ART17 PO7978 09/113,067 ART18 PO7982 09/113,063 ART19 PO7989 09/113,069 ART20 PO8019 09/112,744 ART21 PO7980  6,356,715 ART22 PO8018 09/112,777 ART24 PO7938 09/113,224 ART25 PO8016  6,366,693 ART26 PO8024 09/112,805 ART27 PO7940 09/113,072 ART28 PO7939 09/112,785 ART29 PO8501  6,137,500 ART30 PO8500 09/112,796 ART31 PO7987 09/113,071 ART32 PO8022 09/112,824 ART33 PO8497 09/113,090 ART34 PO8020 09/112,823 ART38 PO8023 09/113,222 ART39 PO8504 09/112,786 ART42 PO8000 09/113,051 ART43 PO7977 09/112,782 ART44 PO7934 09/113,056 ART45 PO7990 09/113,059 ART46 PO8499 09/113,091 ART47 PO8502  6,381,361 ART48 PO7981  6,317,192 ART50 PO7986 09/113,057 ART51 PO7983 09/113,054 ART52 PO8026 09/112,752 ART53 PO8027 09/112,759 ART54 PO8028 09/112,757 ART56 PO9394  6,357,135 ART57 PO9396 09/113,107 ART58 PO9397  6,271,931 ART59 PO9398  6,353,772 ART60 PO9399  6,106,147 ART61 PO9400 09/112,790 ART62 PO9401  6,304,291 ART63 PO9402 09/112,788 ART64 PO9403  6,305,770 ART65 PO9405  6,289,262 ART66 PP0959  6,315,200 ART68 PP1397  6,217,165 ART69 PP2370 09/112,781 DOT01 PP2371 09/113,052 DOT02 PO8003  6,350,023 Fluid01 PO8005  6,318,849 Fluid02 PO9404 09/113,101 Fluid03 PO8066  6,227,652 IJ01 PO8072  6,213,588 IJ02 PO8040  6,213,589 IJ03 PO8071  6,231,163 IJ04 PO8047  6,247,795 IJ05 PO8035  6,394,581 IJ06 PO8044  6,244,691 IJ07 PO8063  6,257,704 IJ08 PO8057  6,416,168 IJ09 PO8056  6,220,694 IJ10 PO8069  6,257,705 IJ11 PO8049  6,247,794 IJ12 PO8036  6,234,610 IJ13 PO8048  6,247,793 IJ14 PO8070  6,264,306 IJ15 PO8067  6,241,342 IJ16 PO8001  6,247,792 IJ17 PO8038  6,264,307 IJ18 PO8033  6,254,220 IJ19 PO8002  6,234,611 IJ20 PO8068  6,302,528 IJ21 PO8062  6,283,582 IJ22 PO8034  6,239,821 IJ23 PO8039  6,338,547 IJ24 PO8041  6,247,796 IJ25 PO8004 09/113,122 IJ26 PO8037  6,390,603 IJ27 PO8043  6,362,843 IJ28 PO8042  6,293,653 IJ29 PO8064  6,312,107 IJ30 PO9389  6,227,653 IJ31 PO9391  6,234,609 IJ32 PP0888  6,238,040 IJ33 PP0891  6,188,415 IJ34 PP0890  6,227,654 IJ35 PP0873  6,209,989 IJ36 PP0993  6,247,791 IJ37 PP0890  6,336,710 IJ38 PP1398  6,217,153 IJ39 PP2592  6,416,167 IJ40 PP2593  6,243,113 IJ41 PP3991  6,283,581 IJ42 PP3987  6,247,790 IJ43 PP3985  6,260,953 IJ44 PP3983  6,267,469 IJ45 PO7935  6,224,780 IJM01 PO7936  6,235,212 IJM02 PO7937  6,280,643 IJM03 PO8061  6,284,147 IJM04 PO8054  6,214,244 IJM05 PO8065  6,071,750 IJM06 PO8055  6,267,905 IJM07 PO8053  6,251,298 IJM08 PO8078  6,258,285 IJM09 PO7933  6,225,138 IJM10 PO7950  6,241,904 IJM11 PO7949 09/113,129 IJM12 PO8060 09/113,124 IJM13 PO8059  6,231,773 IJM14 PO8073  6,190,931 IJM15 PO8076  6,248,249 IJM16 PO8075 09/113,120 IJM17 PO8079  6,241,906 IJM18 PO8050 09/113,116 IJM19 PO8052  6,241,905 IJM20 PO7948 09/113,117 IJM21 PO7951  6,231,772 IJM22 PO8074  6,274,056 IJM23 PO7941 09/113,110 IJM24 PO8077  6,248,248 IJM25 PO8058 09/113,087 IJM26 PO8051 09/113,074 IJM27 PO8045  6,110,754 IJM28 PO7952 09/113,088 IJM29 PO8046 09/112,771 IJM30 PO9390  6,264,849 IJM31 PO9392  6,254,793 IJM32 PP0889  6,235,211 IJM35 PP0887 09/112,801 IJM36 PP0882  6,264,850 IJM37 PP0874  6,258,284 IJM38 PP1396 09/113,098 IJM39 PP3989  6,228,668 IJM40 PP2591  6,180,427 IJM41 PP3990  6,171,875 IJM42 PP3986  6,267,904 IJM43 PP3984  6,245,247 IJM44 PP3982 09/112,835 IJM45 PP0895  6,231,148 IR01 PP0870 09/113,106 IR02 PP0869 09/113,105 IR04 PP0887 09/113,104 IR05 PP0885  6,238,033 IR06 PP0884 09/112,766 IR10 PP0886  6,238,111 IR12 PP0871 09/113,086 IR13 PP0876 09/113,094 IR14 PP0877 09/112,760 IR16 PP0878  6,196,739 IR17 PP0879 09/112,774 IR18 PP0883  6,270,182 IR19 PP0880  6,152,619 IR20 PP0881 09/113,092 IR21 PO8006  6,087,638 MEMS02 PO8007 09/113,093 MEMS03 PO8008 09/113,062 MEMS04 PO8010  6,041,600 MEMS05 PO8011 09/113,082 MEMS06 PO7947  6,067,797 MEMS07 PO7944 09/113,080 MEMS09 PO7946  6,044,646 MEMS10 PO9393 09/113,065 MEMS11 PP0875 09/113,078 MEMS12 PP0894 09/113,075 MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

FIELD OF THE INVENTION

[0003] The present invention relates to the field of inkjet printing and, in particular, discloses a method of manufacturing a micro-electromechanical fluid ejecting device.

BACKGROUND OF THE INVENTION

[0004] Many ink jet printing mechanisms are known. Unfortunately, in mass production techniques, the production of ink jet heads is quite difficult. For example, often, the orifice or nozzle plate is constructed separately from the ink supply and ink ejection mechanism and bonded to the mechanism at a later stage (Hewlett-Packard Journal, Vol. 36 no 5, pp 33-37 (1985)). The separate material processing steps required in handling such precision devices often add a substantial expense in manufacturing.

[0005] Additionally, side shooting ink jet technologies (U.S. Pat. No. 4,899,181) are often used but again, this limits the amount of mass production throughput given any particular capital investment.

[0006] Additionally, more esoteric techniques are also often utilized. These can include electroforming of nickel stage (Hewlett-Packard Journal, Vol. 36 no 5, pp 33-37 (1985)), electro-discharge machining, laser ablation (U.S. Pat. No. 5,208,604), micro-punching, etc.

[0007] The utilization of the above techniques is likely to add substantial expense to the mass production of ink jet print heads and therefore add substantially to their final cost.

[0008] It would therefore be desirable if an efficient system for the mass production of ink jet print heads could be developed.

SUMMARY OF THE INVENTION

[0009] In accordance with a first aspect of the present invention, there is provided a method of manufacturing a Dual Chamber Single Vertical Actuator Ink Jet Printer print head wherein an array of nozzles are formed on a substrate utilizing planar monolithic deposition, lithographic and etching processes. Preferably, multiple ink jet heads are formed simultaneously on a single planar substrate such as a silicon wafer.

[0010] The print heads can be formed utilizing standard vlsi/ulsi processing and can include integrated drive electronics formed on the same substrate. The drive electronics preferably being of a CMOS type. In the final construction, ink can be ejected from the substrate substantially normal to the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0012]FIG. 1 shows a schematic side view of an ink jet nozzle of the invention in a quiescent state;

[0013]FIG. 2 shows a schematic side view of the nozzle in an initial part of an ink ejection stage;

[0014]FIG. 3 shows a schematic side view of the nozzle in a further part of an ink ejection stage;

[0015]FIG. 4 shows a schematic side view of the nozzle in a final part of an ink ejection stage;

[0016]FIG. 5 shows a schematic side view of the nozzle again in its quiescent state;

[0017]FIG. 6 illustrates a side perspective view, of a single nozzle arrangement of the preferred embodiment.

[0018]FIG. 7 illustrates a perspective view, partly in section of a single nozzle arrangement of the preferred embodiment;

[0019]FIG. 8 shows a schematic side view of an initial stage in the manufacture of an ink jet nozzle of the invention with the deposition of a CMOS layer;

[0020]FIG. 9 shows a step of an initial etch to form a nozzle chamber;

[0021]FIG. 10 shows a step of depositing a first sacrificial layer;

[0022]FIG. 11 shows a step of etching the first sacrificial layer;

[0023]FIG. 12 shows a step of depositing a glass layer;

[0024]FIG. 13 shows a step of etching the glass layer;

[0025]FIG. 14 shows a step of depositing an actuator material layer;

[0026]FIG. 15 shows a step of planarizing the actuating material layers;

[0027]FIG. 16 shows a step of depositing a heater material layer;

[0028]FIG. 17 shows a step of depositing a further glass layer;

[0029]FIG. 18 shows a step of depositing a further heater material layer;

[0030]FIG. 19 shows a step of planarizing the further heater material layer;

[0031]FIG. 20 shows a step of depositing yet another glass layer;

[0032]FIG. 21 shows a step of etching said another glass layer;

[0033]FIG. 22 shows a step of etching the other glass layers;

[0034]FIG. 23 shows a step of depositing a further sacrificial layer;

[0035]FIG. 24 shows a step of forming a nozzle chamber;

[0036]FIG. 25 shows a step of forming nozzle openings;

[0037]FIG. 26 shows a step of back etching the substrate; and

[0038]FIG. 27 shows a final step of etching the sacrificial layers;

[0039]FIG. 28 illustrates a part of an array view of a portion of a printhead as constructed in accordance with the principles of the present invention;

[0040]FIG. 29 provides a legend of the materials indicated in FIGS. 30 to 42; and

[0041]FIG. 30 shows a sectional side view of an initial manufacturing step of an ink jet printhead nozzle showing a silicon wafer with a buried epitaxial layer and an electrical circuitry layer;

[0042]FIG. 31 shows a step of etching the oxide layer;

[0043]FIG. 32 shows a step of etching an exposed part of the silicon layer;

[0044]FIG. 33 shows a step of depositing a second sacrificial layer;

[0045]FIG. 34 shows a step of etching the first sacrificial layer;

[0046]FIG. 35 shows a step of etching the second sacrificial layer;

[0047]FIG. 36 shows the step of depositing a heater material layer;

[0048]FIG. 37 shows a step of depositing a further heater material layer;

[0049]FIG. 38 shows a step of etching a glass layer;

[0050]FIG. 39 shows a step of depositing a further glass layer;

[0051]FIG. 40 shows a step of etching the further glass layer;

[0052]FIG. 41 shows a step of further etching the further glass layer;

[0053]FIG. 42 shows a step of back etching through the silicon layer;

[0054]FIG. 43 shows a step of etching the sacrificial layers; and

[0055]FIG. 44 shows a step of filling the completed ink jet nozzle with ink.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

[0056] In the preferred embodiment, there is provided an inkjet printhead having an array of nozzles wherein the nozzles are grouped in pairs and each pair is provided with a single actuator which is actuated so as to move a paddle type mechanism to force the ejection of ink out of one or other of the nozzle pairs. The paired nozzles eject ink from a single nozzle chamber which is re-supplied by means of an ink supply channel. Further, the actuator of the preferred embodiment has unique characteristics so as to simplify the actuation process.

[0057] Turning initially to FIGS. 1 to 5, there will now be explained the principles of operation of the preferred embodiment. In the preferred embodiment, a single nozzle chamber 1 is utilized to supply ink to two ink ejection nozzles 2, 3. Ink is re-supplied to the nozzle chamber 1 via means of an ink supply channel 5. In its quiescent position, two ink menisci 6, 7 are formed around the ink ejection holes 2, 3. The arrangement of FIG. 1 being substantially axially symmetric around a central paddle 9 which is attached to an actuator mechanism.

[0058] When it is desired to eject ink out of one of the nozzles, say nozzle 3, the paddle 9 is actuated so that it begins to move as indicated in FIG. 2. The movement of paddle 9 in the direction 10 results in a general compression of the ink on the right hand side of the paddle 9. The compression of the ink results in the meniscus 7 growing as the ink is forced out of the nozzles 3. Further, the meniscus 6 undergoes an inversion as the ink is sucked back on the left hand side of the actuator 10 with additional ink 12 being sucked in from ink supply channel 5. The paddle actuator 9 eventually comes to rest and begins to return as illustrated in FIG. 3. The ink 13 within meniscus 7 has substantial forward momentum and continues away from the nozzle chamber whilst the paddle 9 causes ink to be sucked back into the nozzle chamber. Further, the surface tension on the meniscus 6 results in further in flow of the ink via the ink supply channel 5. The resolution of the forces at work in the resultant flows results in a general necking and subsequent breaking of the meniscus 7 as illustrated in FIG. 4 wherein a drop 14 is formed which continues onto the media or the like. The paddle 9 continues to return to its quiescent position.

[0059] Next, as illustrated in FIG. 5, the paddle 9 returns to its quiescent position and the nozzle chamber refills by means of surface tension effects acting on meniscuses 6, 7 with the arrangement of returning to that showing in FIG. 1. When required, the actuator 9 can be activated to eject ink out of the nozzle 2 in a symmetrical manner to that described with reference to FIGS. 1-5. Hence, a single actuator 9 is activated to provide for ejection out of multiple nozzles. The dual nozzle arrangement has a number of advantages including in that movement of actuator 9 does not result in a significant vacuum forming on the back surface of the actuator 9 as a result of its rapid movement. Rather, meniscus 6 acts to ease the vacuum and further acts as a “pump” for the pumping of ink into the nozzle chamber. Further, the nozzle chamber is provided with a lip 15 (FIG. 2) which assists in equalizing the increase in pressure around the ink ejection holes 3 which allows for the meniscus 7 to grow in an actually symmetric manner thereby allowing for straight break off of the drop 14.

[0060] Turning now to FIGS. 6 and 7, there is illustrated a suitable nozzle arrangement with FIG. 6 showing a single side perspective view and FIG. 7 showing a view, partly in section illustrating the nozzle chamber. The actuator 20 includes a pivot arm attached at the post 21. The pivot arm includes an internal core portion 22 which can be constructed from glass. On each side 23, 24 of the internal portion 22 is two separately control heater arms which can be constructed from an alloy of copper and nickel (45% copper and 55% nickel). The utilization of the glass core is advantageous in that it has a low coefficient thermal expansion and coefficient of thermal conductivity. Hence, any energy utilized in the heaters 23, 24 is substantially maintained in the heater structure and utilized to expand the heater structure and opposed to an expansion of the glass core 22. Structure or material chosen to form part of the heater structure preferably has a high “bend efficiency”. One form of definition of bend efficiency can be the Young's modulus times the coefficient of thermal expansion divided by the density and by the specific heat capacity.

[0061] The copper nickel alloy in addition to being conductive has a high coefficient of thermal expansion, a low specific heat and density in addition to a high Young's modulus. It is therefore a highly suitable material for construction of the heater element although other materials would also be suitable.

[0062] Each of the heater elements can comprise a conductive out and return trace with the traces being insulated from one and other along the length of the trace and conductively joined together at the far end of the trace. The current supply for the heater can come from a lower electrical layer via the pivot anchor 21. At one end of the actuator 20, there is provided a bifurcated portion 30 which has attached at one end thereof to leaf portions 31, 32.

[0063] To operate the actuator, one of the arms 23, 24 e.g. 23 is heated in air by passing current through it. The heating of the arm results in a general expansion of the arm. The expansion of the arm results in a general bending of the arm 20. The bending of the arm 20 further results in leaf portion 32 pulling on the paddle portion 9. The paddle 9 is pivoted around a fulcrum point by means of attachment to leaf portions 38, 39 which are generally thin to allow for minor flexing. The pivoting of the arm 9 causes ejection of ink from the nozzle hole 40. The heater is deactivated resulting in a return of the actuator 20 to its quiescent position and its corresponding return of the paddle 9 also to is quiescent position. Subsequently, to eject ink out of the other nozzle hole 41, the heater 24 can be activated with the paddle operating in a substantially symmetric manner.

[0064] It can therefore be seen that the actuator can be utilized to move the paddle 9 on demand so as to eject drops out of the ink ejection hole e.g. 40 with the ink refilling via an ink supply channel 44 located under the paddle 9.

[0065] The nozzle arrangement of the preferred embodiment can be formed on a silicon wafer utilizing standard semi-conductor fabrication processing steps and micro-electromechanical systems (MEMS) construction techniques.

[0066] For a general introduction to a micro-electro mechanical system (MEMS) reference is made to standard proceedings in this field including the proceeding of the SPIE (International Society for Optical Engineering) including volumes 2642 and 2882 which contain the proceedings of recent advances and conferences in this field.

[0067] Preferably, a large wafer of printheads is constructed at any one time with each printhead providing a predetermined pagewidth capabilities and a single printhead can in turn comprise multiple colors so as to provide for full color output as would be readily apparent to those skilled in the art.

[0068] Turning now to FIG. 8-FIG. 27 there will now be explained one form of fabrication of the preferred embodiment. The preferred embodiment can start as illustrated in FIG. 8 with a CMOS processed silicon wafer 50 which can include a standard CMOS layer 51 including of the relevant electrical circuitry etc. The processing steps can then be as follows:

[0069] 1. As illustrated in FIG. 9, a deep etch of the nozzle chamber 98 is performed to a depth of 25 micron;

[0070] 2. As illustrated in FIG. 10, a 27 micron layer of sacrificial material 52 such as aluminum is deposited;

[0071] 3. As illustrated in FIG. 11, the sacrificial material is etched to a depth of 26 micron using a glass stop so as to form cavities using a paddle and nozzle mask.

[0072] 4. As illustrated in FIG. 12, a 2 micron layer of low stress glass 53 is deposited.

[0073] 5. As illustrated in FIG. 13, the glass is etched to the aluminum layer utilizing a first heater via mask.

[0074] 6. As illustrated in FIG. 14, a 2-micron layer of 60% copper and 40% nickel is deposited 55 and planarized (FIG. 15) using chemical mechanical planarization (CMP).

[0075] 7. As illustrated in FIG. 16, a 0.1 micron layer of silicon nitride is deposited 56 and etched using a heater insulation mask.

[0076] 8. As illustrated in FIG. 17, a 2-micron layer of low stress glass 57 is deposited and etched using a second heater mask.

[0077] 9. As illustrated in FIG. 18, a 2-micron layer of 60% copper and 40% nickel 58 is deposited and planarized (FIG. 19) using chemical mechanical planarization.

[0078] 10. As illustrated in FIG. 20, a 1-micron layer of low stress glass 60 is deposited and etched (FIG. 21) using a nozzle wall mask.

[0079] 11. As illustrated in FIG. 22, the glass is etched down to the sacrificial layer using an actuator paddle wall mask.

[0080] 12. As illustrated in FIG. 23, a 5-micron layer of sacrificial material 62 is deposited and planarized using CMP.

[0081] 13. As illustrated in FIG. 24, a 3-micron layer of low stress glass 63 is deposited and etched using a nozzle rim mask.

[0082] 14. As illustrated in FIG. 25, the glass is etched down to the sacrificial layer using nozzle mask.

[0083] 15. As illustrated in FIG. 26, the wafer can be etched from the back using a deep silicon trench etcher such as the Silicon Technology Systems deep trench etcher.

[0084] 16. Finally, as illustrated in FIG. 27, the sacrificial layers are etched away releasing the ink jet structure.

[0085] Subsequently, the print head can be washed, mounted on an ink chamber, relevant electrical interconnections TAB bonded and the print head tested.

[0086] Turning now to FIG. 28, there is illustrated a portion 80 of a full color printhead which is divided into three series of nozzles 71, 72 and 73. Each series can supply a separate color via means of a corresponding ink supply channel. Each series is further subdivided into two sub rows e.g. 76, 77 with the relevant nozzles of each sub row being fired simultaneously with one sub row being fired a predetermined time after a second sub row such that a line of ink drops is formed on a page.

[0087] As illustrated in FIG. 28 the actuators are formed in a curved relationship with respect to the main nozzle access so as to provide for a more compact packing of the nozzles. Further, the block portion (21 of FIG. 6) is formed in the wall of an adjacent series with the block portion of the row 73 being formed in a separate guide rail 80 provided as an abutment surface for the TAB strip when it is abutted against the guide rail 80 so as to provide for an accurate registration of the tab strip with respect to the bond pads 81, 82 which are provided along the length of the printhead so as to provide for low impedance driving of the actuators.

[0088] The principles of the preferred embodiment can obviously be readily extended to other structures. For example, a fulcrum arrangement could be constructed which includes two arms which are pivoted around a thinned wall by means of their attachment to a cross bar. Each arm could be attached to the central cross bar by means of similarly leafed portions to that shown in FIG. 6 and FIG. 7. The distance between a first arm and the thinned wall can be L units whereas the distance between the second arm and wall can be NL units. Hence, when a translational movement is applied to the second arm for a distance of N×X units the first arm undergoes a corresponding movement of X units. The leafed portions allow for flexible movement of the arms whilst providing for full pulling strength when required.

[0089] It would be evident to those skilled in the art that the present invention can further be utilized in either mechanical arrangement requiring the application forces to induce movement in a structure.

[0090] One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:

[0091] 1. Using a double sided polished wafer 50, complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process 51. Relevant features of the wafer at this step are shown in FIG. 30. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. FIG. 29 is a key to representations of various materials in these manufacturing diagrams, and those of other cross-referenced ink jet configurations.

[0092] 2. Etch oxide down to silicon or aluminum using Mask 1. This mask defines the ink inlet, the heater contact vias, and the edges of the print head chips. This step is shown in FIG. 31.

[0093] 3. Etch exposed silicon 51 to a depth of 20 microns. This step is shown in FIG. 32.

[0094] 4. Deposit a 1-micron conformal layer of a first sacrificial material 91.

[0095] 5. Deposit 20 microns of a second sacrificial material 92, and planarize down to the first sacrificial layer using CMP. This step is shown in FIG. 33.

[0096] 6. Etch the first sacrificial layer using Mask 2, defining the nozzle chamber wall 93, the paddle 9, and the actuator anchor point 21. This step is shown in FIG. 34.

[0097] 7. Etch the second sacrificial layer down to the first sacrificial layer using Mask 3. This mask defines the paddle 9. This step is shown in FIG. 35.

[0098] 8. Deposit a 1-micron conformal layer of PECVD glass 53.

[0099] 9. Etch the glass using Mask 4, which defines the lower layer of the actuator loop.

[0100] 10. Deposit 1 micron of heater material 55, for example titanium nitride (TiN) or titanium diboride (TiB2). Planarize using CMP. This step is shown in FIG. 36.

[0101] 11. Deposit 0.1 micron of silicon nitride 56.

[0102] 12. Deposit 1 micron of PECVD glass 57.

[0103] 13. Etch the glass using Mask 5, which defines the upper layer of the actuator loop.

[0104] 14. Etch the silicon nitride using Mask 6, which defines the vias connecting the upper layer of the actuator loop to the lower layer of the actuator loop.

[0105] 15. Deposit 1 micron of the same heater material 58 previously deposited. Planarize using CMP. This step is shown in FIG. 37.

[0106] 16. Deposit 1 micron of PECVD glass 60.

[0107] 17. Etch the glass down to the sacrificial layer using Mask 6. This mask defines the actuator and the nozzle chamber wall, with the exception of the nozzle chamber actuator slot. This step is shown in FIG. 38.

[0108] 18. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated.

[0109] 19. Deposit 4 microns of sacrificial material 62 and planarize down to glass using CMP.

[0110] 20. Deposit 3 microns of PECVD glass 63. This step is shown in FIG. 39.

[0111] 21. Etch to a depth of (approx.) 1 micron using Mask 7. This mask defines the nozzle rim 95. This step is shown in FIG. 40.

[0112] 22. Etch down to the sacrificial layer using Mask 8. This mask defines the roof of the nozzle chamber, and the nozzle 40, 41 itself. This step is shown in FIG. 41.

[0113] 23. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask 9. This mask defines the ink inlets 65 which are etched through the wafer. The wafer is also diced by this etch. This step is shown in FIG. 42.

[0114] 24. Etch both types of sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in FIG. 43.

[0115] 25. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink 96 to the ink inlets at the back of the wafer.

[0116] 26. Connect the print heads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper.

[0117] 27. Hydrophobize the front surface of the print heads.

[0118] 28. Fill the completed print heads with ink and test them. A filled nozzle is shown in FIG. 44.

[0119] The presently disclosed ink jet printing technology is potentially suited to a wide range of printing system including: color and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printers, low cost scanning printers high speed pagewidth printers, notebook computers with in-built pagewidth printers, portable color and monochrome printers, color and monochrome copiers, color and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic “minilabs”, video printers, PhotoCD printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays.

[0120] It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.

[0121] Ink Jet Technologies

[0122] The embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. However presently popular ink jet printing technologies are unlikely to be suitable.

[0123] The most significant problem with thermal ink jet is power consumption. This is approximately 100 times that required for high speed, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal ink jet applications. This leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.

[0124] The most significant problem with piezoelectric ink jet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per print head, but is a major impediment to the fabrication of pagewidth print heads with 19,200 nozzles.

[0125] Ideally, the ink jet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications. To meet the requirements of digital photography, new ink jet technologies have been created. The target features include:

[0126] low power (less than 10 Watts)

[0127] High-resolution capability (1,600 dpi or more)

[0128] photographic quality output

[0129] low manufacturing cost

[0130] small size (pagewidth times minimum cross section)

[0131] high speed (<2 seconds per page).

[0132] All of these features can be met or exceeded by the ink jet systems described below with differing levels of difficulty. Forty-five different ink jet technologies have been developed by the Assignee to give a wide range of choices for high volume manufacture. These technologies form part of separate applications assigned to the present Assignee as set out in the table above under the heading Cross References to Related Applications.

[0133] The ink jet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems

[0134] For ease of manufacture using standard process equipment, the print head is designed to be a monolithic 0.5-micron CMOS chip with MEMS post processing. For color photographic applications, the print head is 100 mm long, with a width which depends upon the ink jet type. The smallest print head designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The print heads each contain 19,200 nozzles plus data and control circuitry.

[0135] Ink is supplied to the back of the print head by injection molded plastic ink channels. The molding requires 50-micron features, which can be created using a lithographically micro machined insert in a standard injection-molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The print head is connected to the camera circuitry by tape automated bonding.

[0136] Tables of Drop-on-Demand Ink Jets

[0137] Eleven important characteristics of the fundamental operation of individual ink jet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee.

[0138] The following tables form the axes of an eleven dimensional table of ink jet types.

[0139] Actuator mechanism (18 types)

[0140] Basic operation mode (7 types)

[0141] Auxiliary mechanism (8 types)

[0142] Actuator amplification or modification method (17 types)

[0143] Actuator motion (19 types)

[0144] Nozzle refill method (4 types)

[0145] Method of restricting back-flow through inlet (10 types)

[0146] Nozzle clearing method (9 types)

[0147] Nozzle plate construction (9 types)

[0148] Drop ejection direction (5 types)

[0149] Ink type (7 types)

[0150] The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of ink jet nozzle. While not all of the possible combinations result in a viable ink jet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain ink jet types have been investigated in detail. These are designated IJ01 to IJ45 which matches the docket numbers in the table under the heading CROSS REFERENCES TO RELATED APPLICATIONS.

[0151] Other ink jet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJ01 to IJ45 examples can be made into ink jet print heads with characteristics superior to any currently available ink jet technology.

[0152] Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The IJ01 to IJ45 series are also listed in the examples column. In some cases, a printer may be listed more than once in a table, where it shares characteristics with more than one entry.

[0153] Suitable applications for the ink jet technologies include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc.

[0154] The information associated with the aforementioned 11 dimensional matrix is set out in the following tables. Description Advantages Disadvantages Examples ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) Thermal An electrothermal heater Large force generated High power Canon Bubblejet 1979 Endo bubble heats the ink to above Simple construction Ink carrier limited to water et al GB patent 2,007,162 boiling point, transferring No moving parts Low efficiency Xerox heater-in-pit 1990 significant heat to the aqueous Fast operation High temperatures required Hawkins et al ink. A bubble nucleates and Small chip area required for High mechanical stress U.S. Pat. No. 4,899,181 quickly forms, expelling the ink. actuator Unusual materials required Hewlett-Packard TIJ 1982 The efficiency of the process is Large drive transistors Vaught et al low, with typically less than Cavitation causes actuator U.S. Pat. No. 4,490,728 0.05% of the electrical energy failure being transformed into kinetic Kogation reduces bubble energy of the drop. formation Large print heads are difficult to fabricate Piezoelectric A piezoelectric crystal such as Low power consumption Very large area required for Kyser et al lead lanthanum zirconate (PZT) Many ink types can be used actuator U.S. Pat. No. 3,946,398 is electrically activated, and Fast operation Difficult to integrate with Zoltan U.S. Pat. No. 3,683,212 and either expands, shears, or High efficiency with electronics 1973 Stemme bends to apply pressure to the High voltage drive transistors U.S. Pat. No. 3,747,120 ink, ejecting drops. required Epson Stylus Full pagewidth print heads Tektronix impractical due to actuator size IJ04 Requires electrical poling in high field strengths during manufacture Electrostrictive An electric field is used to Low power consumption Low maximum strain (approx. Seiko Epson, Usui et all activate electrostriction in Many ink types can be used 0.01%) JP 253401/96 relaxor materials such as lead Low thermal expansion Large area required for actuator IJ04 lanthanum zirconate titanate Electric field strength required due to low strain (PLZT) or lead magnesium (approx. 3.5 V/μm) can be Response speed is marginal nobate (PMN). generated without difficulty (˜10 μs) Does not require electrical High voltage drive transistors poling required Full pagewidth print heads impractical due to actuator size Ferroelectric An electric field is used to Low power consumption Difficult to integrate with IJ04 induce a phase transition Many ink types can be used electronics between the antiferroelectric Fast operation (<1 μs) Unusual materials such as (AFE) and ferroelectric (FE) Relatively high longitudinal PLZSnT are required phase. Perovskite materials such strain Actuators require a large area as tin modified lead lanthanum High efficiency zirconate titanate (PLZSnT) Electric field strength of around exhibit large strains of up to 1% 3 V/μm can be readily provided associated with the AFE to FE phase transition Electrastatic Conductive plates are separated Low power consumption Difficult to operate electrostatic IJ02, IJ04 plates by a compressible or fluid Many ink types can be used devices in an aqueous environ- dielectric (usually air). Upon Fast operation ment application of a voltage, the The electrostatic actuator plates attract each other and will normally need to be displace ink, causing drop seperated from the ink ejection. The conductive plates Very large area required to may be in a comb or honeycomb achieve high forces structure, or stacked to increase High voltage drive transistors the surface are and therefore the may be required force. Full pagewidth print heads are not competitive due to actuator size Electrostatic A strong electric field is applied Low current consumption High voltage required 1989 Saito et al, pull on ink to the ink, whereupon electro- Low temperature May be damaged by sparks due U.S. Pat. No. 4,799,068 static attraction accelerates the to air breakdown 1989 Miura et al, ink towards the print medium. Required field strength increase U.S. Pat. No. 4,810,954 as the drop size decreases Tone-jet High voltage drive transistors required Electrostatic field attracts dust Permanent An electromagnet directly Low power consumption Complex fabrication IJ07, IJ10 magnet attracts a permanent magnet, Many ink types can be used Permanent magnetic material electromagnetic displacing ink and causing drop Fast operation such as Neodymium Iron Boron ejection. Rare earth magnets High efficiency (NdFeB) required. with a field strength around 1 Fast extension from single High local currents required Tesla can be used. Examples nozzles to pagewidth print heads Copper metalization should be are: Samarium Cobalt (SaCo) used for long electromigration and magnetic material in the lifetime and low resistivity neodymium iron boron family Pigmented inks are usually (NdFeB, NdDyFeBNb, infeasible NdDyFeB, etc) Operating temperature limited to the Curie temperature (around 540 K) Soft magnetic A solenoid induced a magnetic Low power consumption Complex fabrication IJ01, IJ05, IJ08, IJ10, IJ12, core field in a soft magnetic core Many ink types can be used Materials not usually present IJ14, IJ15, IJ17 electromagnetic or yoke fabricated from a ferrous Fast operation in a CMOS fab such as NiFe, material such as electroplated High efficiency CoNiFe, or CoFe are required iron alloys such as CoNiFe [1], Easy extension from single High local currents required CoFe, or NiFe alloys. Typically, nozzles to pagewidth print heads Copper metallisation should be the soft magnetic material is in used for long electromigration two parts, which are normally lifetime and low resistivity held apart by a spring. When the Electroplating is required solenoid is actuated, the two High saturation flux density is parts attract, displacing the ink. required (2.0-2.1 T is achievable with CoNiFe [1]) Lorenz force The Lorenz force acting on a Low power consumption Force acts as a twisting motion IJ06, IJ11, IJ13, IJ16 current carrying wire in a Many ink types can be used Typically, only a quarter of the magnetic field is utilized. This Fast operation solenoid length provides force allows the magnetic field to be High efficiency in a useful direction supplied externally to the print Easy extension from single High local current required head, for example with rare nozzles to pagewidth print heads Copper metallisation should be earth permanent magnets. Only used for long electro migration the current carrying wire need lifetime and low resistivity be fabricated on the print head, Pigmented inks are usually simplifying materials infeasible requirements. Magneto- The actuator uses the giant Many ink types can be used Force acts as a twisting motion Fischenbeck, striction magnetostrictive effect of Fast operation Unusual material such as U.S. Pat. No. 4,032,929 materials such as Terfenol-D Easy extention from single Terfenol-D are required IJ25 (an alloy of terbium, dysprosium nozzles to pagewidth print heads High local currents required and iron developed at the Naval High force is available Copper metallisation should be Ordnance Laboratory, hence used for long electro migration Ter-Fe-NOL). For best lifetime and low resistivity efficiency, the actuator should Pre-stressing may be required be prestressed to approx. 8 MPa. Surface tension Ink under positive pressure is Low power consumption Requires supplementary force Silverbrook, EP 0771 658 A2 reduction held in a nozzle by surface Simple construction to effect drop separation and related patent applications tension. The surface tension of No unusual materials required Requires special ink surfactants the ink is reduced below the in fabrication Speed may be limited by bubble threshold, causing the High efficiency surfactant properties ink to egress from the nozzle. Easy extension from single nozzles to pagewidth print heads Viscosity The ink viscosity is locally Simple construction Requires supplementary force Silverbrook, EP 0771 658 A2 reduction reduced to select which drops No unusual materials required in to effect drop separation and related patent applications are to be ejected. A viscosity fabrication Requires special ink viscosity reduction can be achieved Easy extension from single properties electrothermally with most inks, nozzles to pagewidth print heads High speed is difficult to achieve but special inks can be Requires oscillating ink pressure engineered for a 100:1 viscosity A high temperature difference reduction. (typically 80 degrees) is required Acoustic An acoustic wave is generated Can operate without a nozzle Complex drive circuitry 1993 Hadimioglu et al, and focussed upon the drop plate Complex fabrication EUP 550,192 ejection region. Low efficiency 1993 Elrod et al, EUP 572,220 Poor control of drop position Poor control of drop volume Thermoelastic An actuator which relies upon Low power consumption Efficient aqueous operation IJ03, IJ09, IJ17, IJ18, IJ19, bend actuator differential thermal expansion Many ink types can be used requires a thermal insulator on IJ20, IJ21, IJ22, IJ23, IJ24, upon Joule heating is used. Simple planar fabrication the hot side IJ27, IJ28, IJ29, IJ30, IJ31, Small chip area required for Corrosion prevention can be IJ32, IJ33, IJ34, IJ35, IJ36, each actuator difficult IJ37, IJ38, IJ39, IJ40, IJ41 Fast operation Pigmented inks may be High efficiency infeasible, as pigment particles CMOS compatible voltages and may jam the bend actuator currents Standard MEMS processes can be used Easy extension from single nozzles to pagewidth print heads High CTE A material with a very high High force can be generated Requires special material (e.g. IJ09, IJ17, IJ18, IJ20, IJ21, Thermoelastic coefficient of thermal expansion Three methods of PTFE PTFE) IJ22, IJ23, IJ24, IJ27, IJ28, actuator (CTE) such as polytetrafluoro- deposition are under develop- Requires a PTFE deposition IJ29, IJ30, IJ31, IJ42, IJ43, ethylene (PTFE) is used. As ment: chemical vapor process, which is not yet IJ44 high CTE materials are usually deposition (CVD), spin coating, standard in ULSI fabs non-conductive, a heater and evaporation PTFE deposition cannot be fabricated from a conductive PTFE is a candidate for low followed with high temperature material is incorporated. A dielectric constant insulation (above 350° C.) processing 50 μm long PTFE bend actuator in ULSI Pigmented inks may be with polysilicon heater and Very low power consumption infeasible, as pigment particles 15 mW power input can provide Many ink types can be used may jam the bend actuator 180 μN force and 10 μm Simple planar fabrication deflection. Actuator motions Small chip are required for each include: actuator Bend Fast operation Push High efficiency Buckle CMOS compatable voltages and Rotate currents East extension from single nozzles to pagewidth print heads Conductive A polymer with a high High force can be generated Requires special materials IJ24 polymer coefficient of thermal expansion Very low power consumption development (High CTE thermoselastic (such as PTFE) is doped with Many inks can be used conductive polymer) actuator conducting substances to Simple planar fabrication Requires a PTFE deposition increase its conductivity to Small chip area required for process, which is not yet about 3 orders of magnitude each actuator standard in ULSI fabs below that of copper. The Fast operation PTFE deposition cannot be conducting polymer expands High efficiency followed with high temperature when resistively heated. CMOS compatible voltages and (above 350° C.) processing Examples of conducting dopants currents Evaporation and CVD include: Easy extension from single deposition techniques cannot Carbon nanotubes nozzles to pagewidth print heads be used Metal fibers Pigmented inks may be Conductive polymers such as infeasible, as pigment particles doped polythiophene may jam the bend actuator Carbon granules Shape memory A shape memory alloy such as High force is available (stresses Fatigue limits maximum number IJ26 alloy TiNi (also known as Nitinol- of hundreds of MPa) of cycles Nickel Titanium alloy developed Large strain is available (more Low strain (1%) is required to at the Naval Ordnance than 3%) extend fatigue resistance Laboratory) is thermally High corrosion resistance Cycle rate limited by heat switched between its weak Simple construction removal martensitic state and its Easy extension from single Requires unusual materials high stiffness austenic state. nozzles to pagewidth print heads (TiNi) The shape of the actuator in Low voltage operation The latent heat of transformation its martensitic state is must be provided deformed relative to the High current operation austenitic shape. The shape Requires prestressing to distort change causes ejection of a the martensitic state drop. Linear Linear magnetic actuators Linear Magentic actuators can Requires unusual semiconductor IJ12 Magnetic include the Linear Induction be constructed with high thrust, materials such as soft magentic Actuator Actuator (LIA), Linear long travel, and high efficiency alloys (e.g. CoNiFe) Permanent Magnet Synchronous using planar semiconductor Some varieties also require Actuator (LPMSA), Linear fabrication techniques permanent magnetic materials Reluctance Synchronous Long actuator travel is available such as Neodymium iron boron Actuator (LRSA), Linear Medium force is available (NdFeB) Switched Reluctance Actuator Low voltage operation Requires complex multi-phase (LSRA), and the Linear Stepper drive circuity Actuator (LSA). High current operation BASIC OPERATION MODE Actuator This is the simplest mode of Simple operation Drop repetition rate is usually Thermal ink jet directly pushes operation: the actuator directly No external fields required limited to around 10 kHz. Piezoelectric ink jet ink supplies sufficient kinetic Satellite drops can be avoided However, this is not funda- IJ01, IJ02, IJ03, IJ04, IJ05, energy to expel the drop. The if drop velocity is less than mental to the method, but is IJ06, IJ07, IJ09, IJ11, IJ12, drop must have a sufficient 4 m/s related to the refill method IJ14, IJ16, IJ20, IJ22, IJ23, velocity to overcome the surface Can be efficient, depending normally used IJ24, IJ25, IJ26, IJ27, IJ28, tension. upon the actuator used All of the drop kinetic energy IJ29, IJ30, IJ31, IJ32, IJ33, must be provided by the IJ34, IJ35, IJ36, IJ37, IJ38, actuator IJ39, IJ40, IJ41, IJ42, IJ43, Satellite drops usually form if IJ44 drop velocity is greater than 4.5 m/s Proximity The drops to be printed are Very simple print head Requires close proximity Silverbrook, EP 0771 658 A2 selected by some manner (e.g. fabrication can be used between the print head and and related patent applications thermally induced surface The drop selection means does the print media or transfer roller tension reduction of pressurized not need to provide the energy May require two print heads ink). Selected drops are required to separate the drop printing alternate rows of the separated from the ink in the from the nozzle image nozzle by contact with the Monolithic color print heads are print medium or a transfer difficult roller. Electrostatic The drops to be printed are Very simple print head Requires very high electrostatic Silverbrook, EP 0771 658 A2 pull on ink selected by some manner (e.g. fabrication can be used field and related patent applications thermally induced surface The drop selection means does Electrostatic field for small Tone-Jet tension reduction of pressurized not need to provide the energy nozzle sizes is above air ink). Selected drops are required to separate the drop breakdown separated from the ink in the from the nozzle Electrostatic field may attract nozzle by a strong electric field. dust. Magnetic The drops to be printed are Very simple print head Requires magnetic ink Silverbrook, EP 0771 658 A2 pull on ink selected by some manner (e.g. fabrication can be used Ink colors other than black are and related patent applications thermally induced surface The drop slection means does difficult tension reduction of pressurized not need to provide the energy Requires very high magnetic ink). Selected drops are required to separate the drop fields separated from the ink in the from the nozzle nozzle by a strong electric field acting on the magnetic ink. Shutter The actuator moves a shutter High speed (>50 kHz) operation Moving parts are required IJ13, IJ17, IJ21 to block ink flow to the nozzle. can be achieved due to reduced Requires ink pressure modulator The ink pressure is pulsed at a refill time Friction and wear must be multiple of the drop ejection Drop timing can be very considered frequency. accurate Striction is possible The actuator energy can be very low Shuttered grill The actuator moves a shutter Actuators with small travel can Moving parts are required IJ08, IJ15, IJ18, IJ19 to block ink flow through a be used Requires ink pressure modulator grill to the nozzle. The shutter Actuators with small force can Friction and wear must be movement need only be equal to be used considered the width of the grill holes. High speed (>50 kHz) operation Striction is possible can be achieved Pulsed A pulsed magnetic field attracts Extremely low energy operation Requires an external pulsed IJ10 magnetic pull an ‘ink pusher’ at the drop is possible magentic field on ink pusher ejection frequency. An actuator No heat dissipation problems Requires special materials for controls a catch, which prevents both the actuator and the ink the ink pusher from moving pusher when a drop is not to be ejected. Complex construction AUXILLIARY MECHANISM (APPLIED TO ALL NOZZLES) None The actuator directly fires the Simplicity of construction Drop ejection energy must be Most ink jets, including ink drop, and there is no Simplicity of operation supplied by individual nozzle piezoelectric and thermal external field or other Small physical size actuator bubble. mechanism required. IJ01, IJ02, IJ03, IJ04, IJ05, IJ07, IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23, IJ24, IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Oscillating ink The ink pressure oscillates, Oscillating ink pressure can Requires external ink pressure Silverbrook, EP 0771 658 A2 pressure providing much of the drop provide a refill pulse allowing oscillator and related patent applications (including ejection energy. The actuator higher operating speed Ink pressure phase and IJ08, IJ13, IJ15, IJ17, IJ18, acoustic selects which drops are to be The actuators may operate with amplitude must be carefully IJ19, IJ21 stimulation) fired by selectivity blocking much lower energy controlled or enabling nozzles. The ink Acoustic lenses can be used to Acoustic reflections in the ink pressure oscillation may be focus the sound on the nozzles chamber must be designed for achieved by vibrating the print head, or preferably by an actuator in the ink supply. Media The print head is placed in Low power Precision assembly required Silverbrook, EP 0771 658 A2 proximity close proximity to the print High accuracy Paper fibers may cause problems and related patent applications medium. Selected drops protrude Simple print head construction Cannot print on rough substrates from the print head further than unselected drops, and contact the print medium. The drop soaks into the medium fast enough to cause drop separation. Transfer roller Drops are printed to a transfer High accuracy Bulky Silverbrook, EP 0771 658 A2 roller instead of straight to the Wide range of print substrates Expensive and related patent applications print medium. A transfer roller can be used Complex construction Tektronix hot melt piezoelectric can also be used for proximity Ink can be dried on the transfer ink jet drop separation. roller Any of the IJ series Electrostatic An electric field is used to Low power Field strength required for Silverbrook, EP 0771 658 A2 accelerate selected drops Simple print head construction separation of small drops is and related patent applications towards the print medium. near or above air breakdown Tone-Jet Direct A magnetic field is used to Low power Requires magnetic ink Silverbrook, EP 0771 658 A2 magnetic field accelerate selected drops of Simple print head construction Requires strong magnetic field and related patent applications magnetic ink towards the print medium. Cross The print head is placed in a Does not require magnetic Requires external magnet IJ06, IJ16 magnetic field constant magnetic field. The materials to be integrated in Current densities may be high, Lorenz force in a current the print head manufacturing resulting in electromigration carrying wire is used to move process problems the actuator. Pulsed A pulsed magnetic field is used Very low power operation is Complex print head construction IJ10 magnetic field to cyclically attract a paddle, possible Magnetic materials required in which pushes on the ink. A Small print head size print head small actuator moves a catch, which selectively prevents the paddle from moving. ACTUATOR AMPLICATION OR MODIFICATION METHOD None No actuator mechanical Operational simplicity Many actuator mechanisms have Thermal Bubble Ink jet amplification is used. The insufficient travel, or IJ01, IJ02, IJ06, IJ07, IJ16, actuator directly drives the insufficient force, to efficiently IJ25, IJ26 drop ejection process. drive the drop ejection process Differential An actuator material expands Provides greater travel in a High stresses are involved Piezoelectric expansion bend more on one side than on the reduced print head area Care must be taken that the IJ03, IJ09, IJ17, IJ18, IJ19, actuator other. The expansion may be materials do not delaminate IJ20, IJ21, IJ22, IJ23, IJ24, thermal, piezoelectric, Residual bend resulting from IJ27, IJ29, IJ30, IJ31, IJ32, magnetostrictive, or other high temperature or high stress IJ33, IJ34, IJ35, IJ36, IJ37, mechanism. The bend actuator during formation IJ38, IJ39, IJ42, IJ43, IJ44 converts a high force low travel actuator mechanism to high travel, lower force mechanism. Transient bend A trilayer bend actuator where Very good temperature stability High stresses are involved IJ40, IJ41 actuator the two outside layers are High speed, as a new drop can Care must be taken that the identical. This cancels bend be fired before heat dissipates materials do no delaminate due to ambient temperatures and Cancels residual stress of residual stress. The actuator formation only responds to transient heating of one side or the other. Reverse spring The actuator loads a spring. Better coupling to the ink Fabrication complexity IJ05, IJ11 When the actuator is turned off, High stress in the spring the spring releases. This can reverse the force/distance curve of the actuator to make it compatible with the force/time requirements of the drop ejection. Actuator stack A series of thin actuators are Increased travel Increased fabrication complexity Some piezoelectric ink jets stacked. This can be appropriate Reduced drive voltage Increased possibility of short IJ04 where actuators require high circuits due to pinholes electric field strength, such as electrostatic and piezelectric actuators. Multiple Multiple smaller actuators are Increases the force available Actuator forces may not add IJ12, IJ13, IJ18, IJ20, IJ22, actuators used simultaneously to move the from an actuator linearly, reducing efficiency IJ28, IJ42, IJ43 ink. Each actuator need provide Multiple actuators can be only a portion of the force positioned to control ink flow required. accurately Linear Spring A linear spring is used to Matches low travel actuator with Requires print head area for the IJ15 transform a motion with small higher travel requirements spring travel and high force into a Non-contact method of motion longer travel, lower force transformation motion. Coiled actuator A bend actuator is coiled to Increases travel Generally restricted to planar IJ17, IJ21, IJ34, IJ35 provide greater travel in a Reduces chip area implementations due to extreme reduced chip area. Planar implementations are fabrication difficulty in other relatively easy to fabricate. orientations. Flexure bend A bend actuator has a small Simple means of increasing Care must be taken not to IJ10, IJ19, IJ33 actuator region near the fixture point, travel of a bend actuator exceed the elastic limit in the which flexes much more readily flexure area than the remainder of the Stess distribution is very uneven actuator. The actuator flexing Difficult to accurately model is effectively converted from with finite element analysis an even coiling to an angular bend, resulting in greater travel of the actuator tip. Catch The actuator controls a small Very low actuator energy Complex construction IJ10 catch. The catch either enables Very small actuator size Requires external force or disables movement of an ink Unsuitable for pigmented inks pusher that is controlled in a bulk manner. Gears Gears can be used to increase Low force, low travel actuators Moving parts are required IJ13 travel at the expense of duration. can be used Several actuator cycles are Circular gears, rack and pinion, Can be fabricated using standard required ratchets, and other gearing surface MEMS processes More complex drive electronics methods can be used. Complex construction Friction, friction, and wear are possible Buckle plate A buckle plate can be used to Very fast movement achievable Must stay within elastic limits S. Hirata et al. “An Ink-jet change a slow actuator into a of the materials for long device Head Using Diaphragm fast motion. It can also convert life Microactuator”, Proc. IEEE a high force, low travel High stresses involved MEMS, Feb. 1996, pp 418-423. actuator into a high travel, Generally high power IJ18, IJ27 medium force motion. requirement Tapered A tapered magnetic pole can Linearizes the magnetic force/ Complex construction IJ14 magnetic pole increase travel at the expense distance curve of force Lever A lever and fulcrum is used to Matches low travel actuator with High stress around the fulcrum IJ32, IJ36, IJ37 transform a motion with small higher travel requirements travel and high force into a Fulcrum area has no linear motion with longer travel and movement, and can be used for lower force. The lever can also a fluid seal reverse the direction of travel. Rotary impeller The actuator is connected to a High mechanical advantage Complex construction IJ28 rotary impeller. A small angular The ratio of force to travel of Unsuitable for pigmented inks deflection of the actuator results the actuator can be matched to in a rotation of the impeller the nozzle requirements by vanes, which push the ink varying the number of impeller against stationary vanes and out vanes of the nozzle. Acoustic lens A refractive or diffractive (e.g. No moving parts Large area required 1993 Hadimioglu et al, EUP zone plate) acoustic lens is used Only relevant for acoustic 550,192 to concentrate sound waves. ink jets 1993 Elrod et al, EUP 572,220 Sharp A sharp point is used to Simple construction Difficult to fabricate using Tone-jet conductive concentrate an electrostatic field. standard VLSI processes for a point surface ejecting ink-jet Only relevant for electrostatic ink jets ACTUATOR MOTION Volume The volume of the actuator Simple construction in the High energy is typically Hewlett-Packard Thermal expansion changes, pushing the ink in case of thermal ink jet required to achieve volume Ink jet all directions. expansion. This leads to Canon Bubblejet thermal stress, cavitation, and kogation in thermal ink jet implementations Linear, normal The actuator moves in a Efficient coupling to ink drops High fabrication complexity IJ01, IJ02, IJ04, IJ07, IJ11, to chip surface direction normal to the print ejected normal to the surface may be required to achieve IJ14 head surface. The nozzle is perpendicular motion typically in the line of movement. Parallel to The actuator moves parallel Suitable for planar fabrication Fabrication complexity IJ12, IJ13, IJ15, IJ33, IJ34, chip surface to the print head surface. Friction IJ35, IJ36 Drop ejection may still be Stiction normal to the surface. Membrane An actuator with a high force The effective area of the Fabrication complexity 1982 Howkins push but small area is used to push actuator becomes the membrane Actuator size U.S. Pat. No. 4,459,601 a stiff membrane that is in area Difficulty of integration in a contact with the ink. VLSI process Rotary The actuator causes the rotation Rotary levers may be used to Device complexity IJ05, IJ08, IJ13, IJ28 of some element, such a grill increase travel May have friction at a pivot or impeller Small chip area requirements point Bend The actuator bends when A very small change in Requires the actuator to be 1970 Kyser et al energized. This may be due to dimensions can be converted made from at least two distinct U.S. Pat. No. 3,946,398 differential thermal expansion, to a large motion. layers, or to have a thermal 1973 Stemme piezoelectric expansion, difference across the actuator U.S. Pat. No. 3,737,120 magnetostriction, or other form IJ03, IJ09, IJ10, IJ19, IJ23, of relative dimensional change. IJ24, IJ25, IJ29, IJ30, IJ31, IJ33, IJ34, IJ35 Swivel The actuator swivels around a Allows operation where the net Inefficient coupling to the ink IJ06 central pivot. This motion is linear force on the paddle is zero motion suitable where there are Small chip area requirements opposite forces applied to opposite sides of the paddle, e.g. Lorenz force. Straighten The actuator is normally bent, Can be used with shape memory Requires careful balance of IJ26, IJ32 and straightens when energized. alloys where the austenic phase stresses to ensure that the is planar quiescent bend is accurate Double bend The actuator bends in one One actuator can be used to Difficult to make the drops IJ36, IJ37, IJ38 direction when one element is power two nozzles. ejected by both bend directions energized, and bends the other Reduce chip size. identical. way when another element is Not sensitive to ambient A small efficiency loss energized. temperature compared to equivalent single bend actuators. Shear Energizing the actuator causes Can increase the effective travel Not readily applicable to other 1985 Fishbeck a shear motion in the actuator of piezoelectric actuators actuator mechanisms U.S. Pat. No. 4,584,590 material. Radial The actuator squeezes an ink Relatively easy to fabricate High force required 1970 Zoltan constriction reservoir, forcing ink from a single nozzles from glass tubing Inefficient U.S. Pat. No. 3,683,212 constricted nozzle. as macroscopic structures Difficult to integrate with VLSI processes Coil/uncoil A coiled actuator uncoils or Easy to fabricate as a planar Difficult to fabricate for non- IJ17, IJ21, IJ34, IJ35 coils more tightly. The motion VLSI process planar devices of the actuator ejects the ink. Small area required, therefore Poor out-of-plane stiffness low cost Bow The actuator bows (or buckles) Can increase the speed of travel Maximum travel is constrained IJ16, IJ18, IJ27 in the middle when energized. Mechanically rigid High force required Push-Pull Two actuators control a shutter. The structure is pinned at both Not readily suitable for ink jets IJ18 One actuator pulls the shutter, ends, so has a high out-of-plane which directly push the ink and the other pushes it. rigidity Curl inwards A set of actuators curl inwards Good fluid flow to the region Design complexity IJ20, IJ42 to reduce the volume of ink behind the actuator increases that they enclose. efficiency Curl outwards A set of actuators curl outwards, Relatively simple construction Relatively large chip area IJ43 pressurizing ink in a chamber surrounding the actuators, and expelling ink from a nozzle in the chamber. Iris Multiple vanes enclose a volume High efficiency High fabrication complexity IJ22 of ink. These simultaneously Small chip area Not suitable for pigmented inks rotate, reducing the volume between the vanes. Acoustic The actuator vibrates at a high The actuator can be physically Large area required for efficient 1993 Hadimioglu et al, vibration frequency. distant from the ink operation at useful frequencies EUP 550,192 Asoustic coupling and crosstalk 1993 Elrod et al EUP 572,220 Complex drive circuitry Poor control of drop volume and position None In various ink jet designs the No moving parts Various other tradeoffs are Silverbrook, EP 0771 658 A2 actuator does not move. required to eliminate moving and related patent applications parts Tone-jet NOZZLE REFILL METHOD Surface tension This is the normal way that ink Fabrication simplicity Low speed Thermal ink jet jets are refilled. After the Operational simplicity Surface tension force relatively Piezoelectric ink jet actuator is energized, it typically small compared to actuator force IJ01-IJ07, IJ10-IJ14, IJ16, returns rapidly to its normal Long refill time usually IJ20, IJ22-IJ45 position. This rapid return sucks dominates the total repetition the air through the nozzle rate opening. The ink surface tension at the nozzle then exerts a small force restoring the meniscus to a minimum area. This force refills the nozzle. Shuttered Ink to the nozzle chamber is High speed Requires common ink pressure IJ08, IJ13, IJ15, IJ17, IJ18, oscillating ink provided at a pressure that Low actuator energy, as the oscillator IJ19, IJ21 pressure oscillates at twice the drop actuator need only open or close May not be suitable for ejection frequency. When a drop the shutter, instead of ejecting pigmented inks is to be ejected, the shutter the ink drop is opened for 3 half cycles: drop ejection, actuator return, and refill. The shutter is then closed to prevent the nozzle chamber emptying during the next negative pressure cycle. Refill actuator After the main actuator has High speed, as the nozzle is Requires two indenpendent IJ09 ejected a drop a second (refill) actively refilled actuators per nozzle actuator is energized. The refill actuator returns slowly, to prevent its return from emptying the chamber again. Positive The ink is held a slight positive High refill rate, therefore a Surface spill must be prevented Silverbrook, EP 0771 658 A2 ink pressure pressure. After the ink drop is high drop repetition rate is Highly hydrophobic print head and related patent applications ejected, the nozzle chamber fills possible surfaces are required Alternative for:, IJ01-IJ07, quickly as surface tension and IJ10-IJ14, IJ16, IJ20, IJ22-IJ45 ink pressure both operate to refill the nozzle. METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Long inlet The ink inlet channel to the Designs simplicity Restricts refill rate Thermal ink jet channel nozzle chamber is made long Operational simplicity May result in a relatively large Piezoelectric ink jet and relatively narrow, relying on Reduces crosstalk chip area IJ42, IJ43 viscous drag to reduce inlet Only partially effective back-flow. Positve The ink is under a positive Drop selection and separation Requires a method (such as a Silverbrook, EP 0771 658 A2 ink pressure pressure, so that in the quiescent forces can be reduced nozzle rim or effective and related patent applications state some of the ink drop Fast refill time hydrophobizing, or both) to Possible operation of the already protrudes from the prevent flooding of the ejection following: IJ01-IJ07, IJ09-IJ12, nozzle. This reduces the surface of the print head. IJ14, IJ16, IJ20, IJ22, IJ23-IJ34 pressure in the nozzle chamber IJ36-IJ41, IJ44 which is required to eject a certain volume of ink. The reduction in chamber pressure results in a reduction in ink pushed out through the inlet. Baffle One or more baffles are placed The refill rate is not as Design complexity HP Thermal Ink Jet in the inlet ink flow. When the restricted as the long inlet May increase fabrication Tektronix piezoelectric ink jet actuator is energized, the rapid method. complexity (e.g. Tektronix hot ink movement creates eddies Reduces crosstalk melt piezoelectric print heads). which restrict the flow through the inlet. The slower refill process is unrestricted, and does not result in eddies. Flexible flap In this method recently disclosed Significantly reduces back-flow Not applicable to most ink jet Canon restricts inlet by Canon, the expanding for edge-shooter thermal ink configurations actuator (bubble) pushes on jet devices Increased fabrication complexity flexible flap that restricts the Inelastic deformation of polymer inlet. flap results in creep over extended use Inlet filter A filter is located between the Additional advantage of ink Restricts refill rate IJ04, IJ12, IJ24, IJ27, IJ29, ink inlet and the nozzle filtration May result in complex IJ30 chamber. The filter has a Ink filter may be fabricated with construction multitude of small holes or slots, no additional process steps restricting ink flow. The filter also removes particles which may block the nozzle. Small inlet The ink inlet channel to the Design simplicity Restricts refill rate IJ02, IJ37, IJ44 compared to nozzle chamber has a sub- May result in a relatively large nozzle stantially smaller cross section chip area than that of the nozzle, Only partially effective resulting in easier ink egress out of the nozzle than out of the inlet. Inlet shutter A secondary actuator controls Increases speed of the ink-jet Requires separate refill actuator IJ09 the position of a shutter, print head operation and drive circuit closing off the ink inlet when the main actuator is energized. The inlet is The method avoids the problem Back-flow problem is eliminated Requires careful design to IJ01, IJ03, IJ05, IJ06, IJ07, located behind of inlet back-flow by arranging minimize the negative pressure IJ10, IJ11, IJ14, IJ16, IJ22, the ink-pushing the ink-pushing surface of behind the paddle IJ23, IJ25, IJ28, IJ31, IJ32, surface the actuator between the inlet IJ33, IJ34, IJ35, IJ36, IJ39, and the nozzle. IJ40, IJ41 Part of the The actuator and a wall of the Significant reductions in Small increases in fabrication IJ07, IJ20, IJ26, IJ38 actuator ink chamber are arranged so that back-flow can be achieved complexity moves to shut the motion of the actuator closes Compact designs possible off the inlet off the inlet. Nozzle In some configuaration of ink Ink back-flow problem is None related to ink back-flow Silverbrook, EP 0771 658 A2 actuator jet, there is no expansion or eliminated on actuation and related patent applications does not movement of an actuator which Valve-jet result in ink may cause ink back-flow Tone-jet back-flow through the inlet. NOZZLE CLEARING METHOD Normal nozzle All of the nozzles are fired No added complexity on the May not be sufficient to Most ink jet systems firing periodically, before the ink has print head displace dried ink IJ01, IJ02, IJ03, IJ04, IJ05, a chance to dry. When not in use IJ06, IJ07, IJ09, IJ10, IJ11, the nozzles are sealed (capped) IJ12, IJ14, IJ16, IJ20, IJ22, against air. The nozzle firing IJ23, IJ24, IJ25, IJ26, IJ27, is usually performed during a IJ28, IJ29, IJ30, IJ31, IJ32, special clearing cycle, after first IJ33, IJ34, IJ36, IJ37, IJ38, moving the print head to a IJ39, IJ40, IJ41, IJ42, IJ43, cleaning station. IJ44, IJ45 Extra power In systems which heat the ink, Can be highly effective if the Requires higher drive voltage Silverbrook, EP 0771 658 A2 to ink heater but do not boil it under normal heater is adjacent to the nozzle for clearing and related patent applications situations, nozzle clearing can May require larger drive be achieved by over-powering transistors the heater and boiling ink at the nozzle. Rapid The actuator is fired in rapid Does not require extra drive Effectiveness depends sub- May be used with: IJ01, IJ02, succession of succession. In some config- circuits on the print head stantially upon the configuration IJ03, IJ04, IJ05, IJ06, IJ07, actuator pulses urations, this may cause heat Can be readily controlled and of the ink jet nozzle IJ09, IJ10, IJ11, IJ14, IJ16, build-up at the nozzle which initiated by digital logic IJ20, IJ22, IJ23, IJ24, IJ25, boils the ink, clearing the IJ27, IJ28, IJ29, IJ30, IJ31, nozzle. In other situations, IJ32, IJ33, IJ34, IJ36, IJ37, it may cause sufficient vibrations IJ38, IJ39, IJ40, IJ41, IJ42, to dislodge clogged nozzles. IJ43, IJ44, IJ45 Extra power to Where an actuator is not A simple solution where Not suitable where there is a May be used with: IJ03, IJ09, ink pushing normally driven to the limit of applicable hard limit to actuator movement IJ16, IJ20, IJ23, IJ24, IJ25 actuator its motion, nozzle clearing may IJ27, IJ29, IJ30, IJ31, IJ32 be assisted by providing an IJ39, IJ40, IJ41, IJ42, IJ43 enhanced drive signal to the IJ44, IJ45 actuator. Acoustic An ultrasonic wave is applied to A high nozzle clearing capability high implementation cost if IJ08, IJ13, IJ15, IJ17, IJ18, resonance the ink chamber. This wave is of can be achieved system does not already include IJ19, IJ21 an appropriate amplitude and May be implemented at very low an acoustic actuator frequency to cause sufficient cost in systems which already force at the nozzle to clear include acoustic actuators blockages. This is easiest to acheive if the ultrasonic wave is at a resonant frequency of the ink cavity. Nozzle clearing A microfabricated plate is Can clear severely clogged Accurate mechanical alignment Silverbrook, EP 0771 658 A2 plate pushed against the nozzles. The nozzles is required and related patent applications plate has a post for every Moving parts are required nozzle. A post moves through There is risk of damage to the each nozzle, displacing dried nozzles ink. Accurate fabrication is required Ink pressure The pressure of the ink is May be effective where other Requires pressure pump or other May be used with all IJ series pulse temporarily increased so that methods cannot be used pressure actuator ink jets ink streams from all of the Expensive nozzles. This may be used in Wasteful of ink conjunction with acuator energizing. Print head A flexible ‘blade’ is wiped Effective for planar print Difficult to use if print head Many ink jet systems wiper across the print head surface. head surfaces surface is non-planar or very The blade is usually fabricated Low cost fragile from a flexible polymer, e.g. Requires mechanical parts rubber or synthetic elastomer. Blade can wear out in high volume print systems Separate ink A seperate heater is provided at Can be effective where other Fabrication complexity Can be used with many IJ series boiling heater the nozzle although the normal nozzle clearing methods cannot ink jets drop ejection mechanism does be used not require it. The heaters do Can be implemented at no not require indiviual drive additional cost in some ink jet circuits, as many nozzles can configurations be cleared simultaneously, and no imaging is required. NOZZLE PLATE CONSTRUCTION Electroformed A nozzle plate is seperately Fabrication simplicity High temperatures and pressures Hewlett Packard Thermal formed fabricated from electrformed are required to bond nozzle plate Ink jet nickel, and bonded to the print Minimum thickness constraints head chip. Differential thermal expansion Laser ablated Individual nozzle holes are No masks required Each hole must be individually Canon Bubblejet or drilled ablated by an intense UV laser Can be quite fast formed 1998 Sercel et al., SPIE, polymer in a nozzle plate, which is Some control over nozzle profile Special equipment required Vol. 998 Excimer Beam typically a polymer such a is possible Slow where there are many Applications, pp. 76-83 polyimide or polysulphone Equipment required is relatively thousands of nozzles per print 1993 Watanabe et al., low cost head U.S. Pat. No. 5,208,604 May produce thin burrs at exit holes Silicon A seperate nozzle plate is High accuracy is attainable Two part construction K. Bean, IEEE Transactions on micromachined micromachined from single High cost Electron Devices, Vol. ED-25, crysal silicon, and bonded to Requires precision alignment No. 10, 1978, pp 1185-1195 the print head wafer. Nozzles may be clogged by Xerox 1990 Hawkins et al., adhesive U.S. Pat. No. 4,899,181 Glass Fine glass capillaries are No expensive equipment Very small nozzle sizes are 1970 Zoltan capillaries drawn from glass tubing. This required difficult to form U.S. Pat. No. 3,683,212 method has been used for Simple to make single nozzles Not suited for mass production making individual nozzles, but is difficult to use for bulk manufacturing of print heads with thousands of nozzles. Monolithic, The nozzle plate is deposited High accuracy (<1 μm) Requires sacrificial layer under Silverbrook, EP 0771 658 A2 surface as a layer using standard VLSI Monolithic the nozzle plate to form the and related patent applications micromachined deposition techniques. Nozzles Low cost nozzle chamber IJ01, IJ02, IJ04, IJ11, IJ12, using VLSI are etched in the nozzle plate Existing processes can be used Surface may be fragile to the IJ17, IJ18, IJ20, IJ22, IJ24, lithographic using VLSI lithography and touch IJ27, IJ28, IJ29, IJ30, IJ31, processes etching IJ32, IJ33, IJ34, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Monolithic, The nozzle plate is a buried High accuracy (<1 μm) Requires long etch times IJ03, IJ05, IJ06, IJ07, IJ08, etched through etch stop in the wafer. Nozzle Monolithic Requires a support wafer IJ09, IJ10, IJ13, IJ14, IJ15, substrate chambers are etched in the front Low cost IJ16, IJ19, IJ21, IJ23, IJ25, of the wafer, and the wafer is No differential expansion IJ26 thinned from the back side. Nozzles are then etched in the etch stop layer. No nozzle plate Various methods have been tried No nozzles to become clogged Difficult to control drop position Ricoh 1995 Sekiya et al to eliminate the nozzles entirely, accurately U.S. Pat. No. 5,412,413 to prevent nozzle clogging. Crosstalk problems 1993 Hadimioglu et al These include thermal bubble EUP 550,192 mechanisms and acoustic lens 1993 Elrod et al mechanisms EUP 572,220 Trough Each drop ejector has a trough Reduced manufacturing Drop firing direction is sensitive IJ35 through which a paddle moves. complexity to wicking. There is no nozzle plate. Monolithic Nozzle slit The elimination of nozzle holes No nozzle to become clogged Difficult to control drop position 1989 Saito et al instead of and replacement by a slit accurately U.S. Pat. No. 4,799,068 individual encompassing many actuator Crosstalk problems nozzles positions reduces nozzle clogging, but increases crosstalk due to ink surface waves DROP EJECTION DIRECTION Edge (‘edge Ink flow is along the surface Simple construction Nozzles limited to edge Canon Bubblejet 1979 Endo shooter’) of the chip, and ink drops are No silicon etching required High resolution is difficult et al GB patent 2,007,162 ejected from the chip edge. Good heat sinking via substrate Fast color printing requires Xerox heater-in-pit 1990 Mechanically strong one print head per color Hawkins et al U.S. Pat. No. Ease of chip handing 4,899,181 Tone-jet Surface (‘roof Ink flow is along the surface No bulk silicon etching required Maximum ink flow is severely Hewlett-Packard TIJ 1982 shooter’) of the chip, and ink drops are Silicon can make an effective restricted Vaught et al ejected from the chip surface, heat sink U.S. Pat. No. 4,490,728 normal to the plane of the chip. Mechanical strength IJ02, IJ11, IJ12, IJ20, IJ22 Through chip, Ink flow is through the chip, High ink flow Requires bulk silicon etching Silverbrook, EP 0771 658 A2 forward and ink drops are ejected from Suitable for pagewidth print and related patent applications (‘up shooter’) the front surface of the chip. heads IJ04, IJ17, IJ18, IJ24, High nozzle packing density IJ27-IJ45 therefore low manufacturing cost Through chip, Ink flow is through the chip, High ink flow Requires wafer thinning IJ01, IJ03, IJ05, IJ06, IJ07 reverse (‘down and ink drops are ejected from Suitable for pagewidth print Requires special handling during IJ08, IJ09, IJ10, IJ13, IJ14 shooter’) the rear surface of the chip. heads manufacturing IJ15, IJ16, IJ19, IJ21, IJ23 High nozzle packing density IJ25, IJ26 therefore low manufacturing cost Through Ink flow is through the actuator, Suitable for piezolelectric print Pagewidth print heads require Epson Stylus actuator which is not fabricated as part head several thousand connections to Tektronix hot melt piezoelectric of the same substrate as the drive cicuits ink jets drive transistors. Cannot be manufactured in standard CMOS fabs Complex assembly required INK TYPE Aqueous, dye Water based ink which typically Environmentally friendly Slow drying Most existing ink jets contains: water, dye, surfactant, No odor Corrosive All IJ series in jets humectant, and biocide. Bleeds on paper Silverbrook, EP 0771 658 A2 Modern ink dyes have high May strikethough and related patent applications water-fastness, light fastness Cockles paper Aqueous, Water based ink which typically Environmentally friendly Slow drying IJ02, IJ04, IJ21, IJ26, IJ27, pigment contains: water, pigment, No odor Corrosive IJ30 surfactant, humectant, and Reduced bleed Pigment may clog nozzles Silverbrook, EP 0771 658 A2 biocide. Pigments have an Reduced wicking pigment may clog actuator and related patent applications advantage in reduced bleed, Reduced strickthough mechanisms Piezoelectric ink-jets wicking and strikethough. Cockles paper Thermal ink jets (with significant restrictions) Methy Ethyl MEK is a highly volatile solvent Very fast drying Odorous All IJ series ink jets Ketone (MEK) used for industrial printing on Prints on various substrates Flammable difficult surfaces such as such as metals and plastics aluminum cans. Alcohol Alcohol based inks can be used Fast drying Slight odor All IJ Series ink jets (ethanol, where the printer must operate Operates as subfreezing Flammable 2-butanol, and at temperatures below the temperatures others) freezing point of water. An Reduced paper cockle example of this is in-camera Low cost consumer photographic printing. Phase change The ink is solid at room No drying time-ink instantly High viscosity Tektronix hot melt (hot melt) temperature, and is melted in the freezes on the print medium Printed ink typically has a piezoelectric ink jets print head before jetting. Hot Almost any print medium can be ‘waxy’ feel 1989 Nowak melt inks are usually wax based, used Printed pages may ‘block’ U.S. Pat. No. 4,820,346 with a melting point around No paper cockle occurs Ink temperature may be above All IJ series ink jets 80° C. After jetting the ink No wicking occurs the curie point of permenant freezes almost instantly upon No bleed occurs magnets contacting the print medium No strikethrough occurs Ink heaters consume power or a transfer roller. Long warm-up time Oil Oil based inks are extensively High solubility medium for High viscosity: this is a All IJ series ink jets used in offset printing. They some dyes significant limitation for use have advantages in improved Does not cockle paper in ink jets, which usually require characteristics on paper Does not wick through paper a low viscosity. Some short (especially no wicking or chain and multi-branched oils cockle). Oil soluble dies and have a sufficiently low viscosity pigments are required. Slow drying Microemulsion A microemulsion is a stable, Stops ink bleed Viscosity higher than water All IJ series ink jets self forming emulsion of oil, High dye solubility Cost is slightly higher than water, and surfactant. The Water, oil, and amphiphilic water based ink characteristic drop size is less soluble dies can be used High surfactant concentration than 100 nm, and is determined Can stabilize pigment required (around 5%) by the preferred curvature of suspensions the surfactant. 

1. A method of manufacturing a micro-electromechanical fluid ejecting device that includes a plurality of nozzle arrangements, each nozzle arrangement defining a nozzle chamber and a pair of fluid ejection ports in fluid communication with the nozzle chamber and a fluid ejecting mechanism operatively positioned with respect to the nozzle chamber to eject fluid from each of the fluid ejection ports, each fluid ejecting mechanism and its corresponding nozzle chamber being configured so that one cycle of operation of the fluid ejecting mechanism results in the ejection of fluid from each of the fluid ejection ports, the method comprising the steps of: forming the plurality of nozzle chambers on a wafer substrate; depositing at least one sacrificial layer on the wafer substrate; forming at least part of each fluid ejecting mechanism on the, or one of the, sacrificial layers; and etching the, or each, sacrificial layer to free the fluid ejecting mechanisms.
 2. A method as claimed in claim 1, in which the step of forming the nozzle chambers includes the step of etching the wafer substrate to define walls of the nozzle chambers.
 3. A method as claimed in claim 2, which includes the step of forming each pair of fluid ejection ports by depositing a roof wall layer on the, or each, sacrificial layer and etching through the roof wall layer.
 4. A method as claimed in claim 1, which includes the step of depositing at least two sacrificial layers so that the sacrificial layers each define deposition zones for components of the fluid ejecting mechanism. 